Method and apparatus for continuous composite three-dimensional printing

ABSTRACT

A method and apparatus for the additive manufacturing of three-dimensional objects are disclosed. Two or more materials are extruded simultaneously as a composite, with at least one material in liquid form and at least one material in a solid continuous strand completely encased within the liquid material. A means of curing the liquid material after extrusion hardens the composite. A part is constructed using a series of extruded composite paths. The strand material within the composite contains specific chemical, mechanical, or electrical characteristics that instill the object with enhanced capabilities not possible with only one material.

RELATED APPLICATIONS

This application is a continuation of, and claims the benefit ofpriority to U.S. application Ser. No. 18/065,568 that was filed on Dec.13, 2022, which is a continuation of, and claims the benefit of priorityfrom U.S. application Ser. No. 16/946,469 that was filed on Jun. 23,2020, which is a continuation of, and claims the benefit of priorityfrom U.S. application Ser. No. 16/460,701 that was filed on Jul. 2,2019, which is based on and claims the benefit of priority from U.S.application Ser. No. 16/401,541 that was filed on May 2, 2019, which isbased on and claims the benefit of priority from U.S. application Ser.No. 15/268,156 filed on Sep. 16, 2016, which is based on and claims thebenefit of priority from U.S. application Ser. No. 13/975,300 that wasfiled on Aug. 24, 2013, which is based on and claims the benefit ofpriority from U.S. Provisional Application No. 61/694,253 that was filedon Aug. 29, 2012, the contents of all of which are expresslyincorporated herein by reference.

BACKGROUND

Additive Manufacturing is a process that creates physical parts from athree-dimensional digital file. The current most common additivemanufacturing techniques include stereo lithography (SLA) and selectivelaser sintering (SLS). These processes build a three-dimensional part byconverting the digital file into several horizontal layers. For the sakeof clarity, this application refers to each layer of an additivemanufactured part created by SLA or SLS as a slice. The base slice iscreated, and then successive slices are added one at a time on top ofeach other, building the part from the bottom up.

SLA performs this method by extruding liquid resin, which is curablewith a UV laser. The resin is extruded first in the base slice, and thena UV light cures and solidifies the slice. Another slice is extrudedatop that slice and cured. This process continues adding slices uponeach other until the part is complete.

SLS uses a reductive technique. A layer of small particles, comparableto powder or sand, is placed on a printing surface. The particles may beplastic, metal, glass, or other material. A laser draws the first sliceof the part in the particles, fusing them together to form the base ofthe part. Another layer of particles is then added across the entireprinting surface. The laser then fuses the newly added particlestogether in the desired shape of the next slice. More particles areadded, and the laser fuses more slices until the entire part is fused.The part is then removed from the loose particles.

Additionally, there are other additive manufacturing techniques similarto SLS that use a binder material, instead of a laser, to fuse particlestogether. It still builds the part with a slicing technique, startingfrom the base and adding slices one at a time.

To strengthen the parts, some additive manufacturing techniques addreinforcing particles. This creates a heterogeneous mixture rather thanpure resin, plastic, or metal. The reinforcing particles are randomlydistributed throughout the part. A comparable application is theaddition of aggregate to cement to create concrete.

The additive manufacturing techniques described above have severaldisadvantages. The process of building parts layer by layer is slow, andnecessitates parts being designed to accommodate the slicing process.The parts are built slice upon slice, with vulnerable joints betweeneach, creating a relatively weak part. Additionally, the materials usedare mostly homogeneous plastic or resin, with a minority ofmanufacturers adding reinforcing particles. These materials have muchroom for improvement with regard to strength and efficiency.

There is a need for a method and apparatus of additive manufacturingthat builds parts faster and easier than the current slicing methods,and also creates stronger parts than the current single or compositematerials in use.

SUMMARY

A method and apparatus for additive manufacturing are described below.The new method is called Continuous Composite Three-Dimensional Printing(CC3D). This method enables the additive manufacturing of partsutilizing two or more materials, and uses an alternate means of buildingparts with paths rather than slices. This affords stronger lighterparts, with flexibility in structure, design, and functionality.Throughout this application, the term part refers to anythree-dimensional object created by additive manufacturing.

The method allows for two or more materials simultaneously incorporatedinto the construction of a part. There is at least one primary materialand at least one secondary material. The primary material is a curableliquid, the best mode being a photosensitive resin. The second materialis a solid strand. The strand may be any material, the best mode beingcarbon fiber. These two materials are extruded together, with thesecondary material fully encased within the primary material.

Together, the primary material and the at least one secondary materialare called the composite material. An extruder emits the compositematerial in a continuous path. As the composite material is extruded, ameans for curing, possibly a UV light, hardens the composite material.

Instead of the slicing method described in the background, the inventionuses a pathing method. A digital model of the part is analyzed andbroken up into paths. A part may contain only one path, or multiplepaths. Each path is one continuous extrusion of the composite material.When a path is completed, the composite material is cut and additionalpaths may be printed to create the part.

The combination of composite material and pathing adds strength to thepart. Slicing creates several layers of a single material stacked uponeach other. Only a chemical bond between slices, or gravity, holds thepart together. By adding a continuous secondary material, an additionalmechanical structure stabilizes the part.

The use of composites also more efficiently uses the primary material.The surface tension created between the secondary and primary materialsallows for the minimal use of primary material. For example, a highercarbon fiber to resin ratio allows parts to be lighter, less costly,stronger, and more flexible. The inclusion of a hollow tube as thesecondary material also has similar weight, flexibility, and efficiencybenefits.

The composite material may be several alternative embodiments. Theprimary material can be any liquid material suitable for extruding andcuring. The secondary material can be any material in the form of astrand. Examples of potential secondary materials include carbon fiber,fiber optics, metal wire, or a hollow rubber tube. Additionally, thesecondary material may be a combination of materials. An example couldbe metal wire within a rubber tube.

The use of CC3D with various composites, allows for increasedflexibility in design and function. Composite material adds strengthduring the manufacturing, allowing paths to extend in three dimensions,rather than only along horizontal planes. This gives the designerflexibility in creating parts.

Additionally, the secondary material provides alternative functions notcurrently supported by additive manufacturing. The use of fiber opticsor other conductive materials in continuous strands, affords thecreation of parts with electronic capabilities. A part may haveintegrated circuitry, or a conductive surface, allowing designers toprint what may be termed intelligent parts and parts with intelligentsurfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a set of example cross-sections of continuous composite paths,showing alternative primary and secondary materials.

FIG. 2 is a section cut of a simple part with multiple paths.

FIG. 3 is a set of example cross-sections of continuous composite paths,showing alternative nozzle shapes.

FIG. 4 is a perspective view of one embodiment of the extruder housing.

FIG. 5 is a perspective view of one embodiment of the extruder housingwith an attached means of curing.

FIG. 6 is a perspective view of a simple part demonstrating the lockingpath process.

FIG. 7 is a perspective view of a simple part composed of severallocking paths.

FIG. 8 is a perspective view of a spiral shaped path.

FIG. 9 contains a perspective view of an extruder forming a tension pathfrom an anchor, and an enlarged perspective view of an anchor, foot, andtension path.

FIG. 10 contains a perspective view and a section cut of an electronicdevice.

FIG. 11 contains a perspective view and a section cut of a boat hull.

DETAILED DESCRIPTION

Continuous Composite Three-Dimensional Printing is a new method ofadditive manufacturing. This method enables the additive manufacturingof parts comprising two or more materials, and uses an alternate meansof building parts with paths rather than slices.

Two or more materials are simultaneously incorporated into theconstruction of a part, creating a composite material path. The simplestembodiment of this method is the use of two materials. The primarymaterial is a liquid curable material, and the secondary material is asolid strand.

The secondary material is fed through a nozzle at the same time that theprimary material is extruded through the nozzle. The secondary materialis fully surrounded by the primary material during the extrusion. Oncethe composite material is extruded it is cured becoming a solidcomposite path.

FIG. 1 shows eight example cross-sections of composite material pathscreated by the method. The primary material in each of these crosssections is a polymer resin. The secondary materials shown includecarbon fiber, fiber optics, metallic wire, and rubber. Eachcross-section has at least one secondary material entirely encasedwithin the primary material. The best mode for a composite materialpath, seen in FIG. 1 , is carbon fiber encased within polymer resin 102.

The apparatus includes a reservoir for containing the primary material,and a means for delivering the primary material to the nozzle uponextrusion. Since primary materials are curable, the reservoir and meansfor delivery should be kept cool and dark as required to prevent curingbefore extrusion.

As show in FIG. 1 , the best mode for the primary material is polymerresin, specifically a single component zero volatile organic compoundresin, but any curable liquid material is included. Potential primarymaterials include epoxy resins, polyester resins, cationic epoxies,acrylated epoxies, urethanes, esters, thermoplastics, photopolymers,polyepoxides, metals, metal alloys, and more.

Interchangeable reservoirs and distribution tubes are included in thebest mode, allowing the apparatus to support the use of multiple primarymaterials for the manufacturing of different parts.

Additionally, the primary material may be a combination of multiplematerials. An example is a two-part epoxy. The two parts are combined ina mixing chamber prior to extrusion and extruded with the secondarymaterial. In this instance, the apparatus will comprise two reservoirsfor the two epoxies, and a mixing chamber connected to the extruder. Themixing chamber applies heat and pressure to the epoxy prior toextrusion.

The apparatus includes a spool or other means of storing the secondarymaterial. The secondary material is a solid strand and flexible enoughto be wound around a spool. It may be a single strand, a tow of severalstrands, a roving of several strands, or multiple strands woventogether. The strands may be any shape, including circular, square, orflat.

FIG. 1 shows multiple examples of possible secondary materials. Includedare carbon fiber, fiber optics, metal wire, and rubber. The strand maybe any solid material. It may be a natural fiber produced by a plant,animal, or geological process. Example natural fibers include vegetablefibers such as cotton, hemp, jute, flax, ramie, rubber, sisal, andbagasse. Wood fibers include groundwood, thermomechanical pulp, andbleached or unbleached kraft or sulfite pulps. Animal fibers includesilk, wool, fur and spidroins. Mineral fibers include chrysotile,amosite, crocidolite, tremolite, anthophyllite, and actinolite.

A six-thousand strand tow of carbon fiber with a diameter ofapproximately one millimeter is the best mode for the secondarymaterial.

Secondary materials may also be composed of synthetic materials.Examples of synthetic materials include metals, metal alloys, aramid,carbon fibers, silicon carbides, fiberglass, petrochemicals, andpolymers.

Pre-impregnating the secondary material is also envisioned. A secondarymaterial is pre-pregged when it is saturated with another material. Anexample is pre-pregged carbon fiber. The carbon fiber is in the form ofa weave, roving, or tow, and is saturated with liquid polymer resin. Thepolymer resin is only partially cured to allow for ease of handling. Itis important to keep this partially cured secondary material cool andaway from light to prevent premature curing prior to extrusion. FIG. 1includes a cross-section of pre-pregged carbon fiber encased withinpolymer resin 101.

Multiple secondary materials may be present in a composite materialpath. The secondary material may be composed of multiple materialsitself, as long as it maintains its strand form. Examples of multiplesecondary materials are included in FIG. 1 . Fiber optics encased inpre-pregged carbon fiber 103, metal wire encased within rubber encasedwithin pre-pregged carbon fiber 105, metal wire encased within fiberoptics encased within carbon fiber 106, rubber encased withinpre-pregged carbon fiber 107, and metal wire encased within pre-preggedcarbon fiber 108. Each of these examples of composite material is alsoencased in a primary material comprising polymer resin.

Another embodiment of the invention includes a secondary material thatis hollow. The secondary material may be a strand that is in the form ofa tube. A rubber tube encased within pre-pregged carbon fiber 107 is anexample of a hollow secondary material. See FIG. 1 . The hollow tube mayserve as a conduit for another substance, or simply left vacant toreduce weight.

It is envisioned that more than one secondary material may be desiredduring the manufacturing of a part. Multiple spools holding multiplesecondary materials are envisioned. A housing and/or loom may be used toprovide variable fiber to the mixing head. Fibers of any kind may beused, spun, sewn, woven together or as a single thread. Flakes of fibermight also be introduced with the liquid as filler. The fiber is notlimited to thread. It may be any combination of elements, and/or rareearths. The secondary materials may feed into the nozzle sequentially sothat a part is comprised of a variety of composite material paths.

The apparatus includes an extruder housing, comprised of an extruder, anozzle, a feeder, and a feeder flap. See FIG. 4 . The extruder 401 isthe location where the liquid primary material is collected before beingextruded out of the nozzle. It may be any shape that facilitates theflow of primary material.

The nozzle is the actual point of extrusion of the composite material402. See FIG. 4 . The best mode for a nozzle is circular, with adiameter of 2 mm. Any size and shape nozzle is envisioned, asnecessitated by the part or economy of manufacture. The cross-sectionsshown in FIG. 1 demonstrate composite paths manufactured with a circularnozzle. FIG. 3 shows three examples of composite paths created withnozzles of alternative shapes, a triangular nozzle 301, a decagon 302,and a rectangle with a secondary material in a tape form 303. Anypolygonal shaped nozzle is envisioned. The nozzle is interchangeable,allowing an apparatus to manufacture parts with different shaped paths,and different sized paths.

The extruder housing also contains a feeder 403, as shown in FIG. 4 .The feeder directs the secondary material to the extruder. The feederconnects to the extruder prior to the nozzle, and feeds the secondarymaterial into the extruder. The secondary material is extruded throughthe nozzle with the primary material, creating a composite materialpath.

The secondary material passes through a feeder flap. The feeder flap 404is a one-way valve that allows the secondary material to enter theextruder, but prevents the primary material from entering the feeder.

The feeder may also have a motorized control dictating the feed rate.Certain embodiments create composite paths with tension, which willnaturally pull the secondary material out through the nozzle. Otherembodiments create paths without tension and require a motor to controlthe feed rate. The motor synchronizes the feed rate with the extrusionrate, the rate at which the primary material is extruded.

Multiple feeders for multiple strands are envisioned, allowing theapparatus to easily alternate between secondary materials during themanufacturing of a part.

The composite material is extruded and then cured. The best mode curesthe composite material immediately after extrusion, creating a solidpath.

There are many potential means of curing, which are determined by theliquid primary material. Possible means of curing include light, heat,and chemical. Ultraviolet light on photosensitive polymer resin is thebest mode. FIG. 5 shows an apparatus with a means of curing attached tothe extruder housing. This figure shows an ultraviolet light 501attached and aimed at the point of extrusion. Other methods of curing bylight include microwave, electron beam, laser, and infrared.Additionally, some primary materials may cure by exposure to naturallight.

The means for curing may also be chemical. If a two-part epoxy is usedas the primary material, the composite path will cure without anyadditional means. Other embodiments include the introduction of acatalyst to the primary material in the extruder. The catalyst beginsthe curing process, and the path hardens soon after extrusion. Theintroduction of heat to a composite path also may aid the curingprocess.

The apparatus may include the means for curing, as in FIG. 5 , or inother embodiments the means for curing may be external. An example maybe a hand held ultraviolet light, or an oven within which to place thepart.

Some embodiments may include multiple means for curing. An example mightbe multiple ultraviolet lights placed around the entire extruder toensure curing of a path created at any angle. An alternative embodimentincludes an ultraviolet light with directional control. It may be angledappropriately during the extrusion of a path to ensure curing throughtight angles and complicated paths.

When a composite material path is complete, the path is cut at the pointof extrusion. Any means of cutting will suffice, including a hand heldblade. Some embodiments of the apparatus include a means for cutting.Possible means include mechanical blades or lasers.

The best mode of the apparatus will have two means of cutting, one forthe secondary material at some point prior to the feeder flap, and onejust after the nozzle. Embodiments with a means of cutting the secondarymaterial afford increased functionality. An alternative secondarymaterial may seamlessly feed into the path, or the path may continuewith only the primary material.

A part may be constructed of one continuous path or may be formed fromseveral paths. FIG. 2 shows a sectional view of a simple part withmultiple paths. When constructing a part, each path is extrudedsequentially. The first path is extruded and cut, and then another pathis extruded and cut, connecting to some portion of the previous path.Additional paths are extruded until the entire part is formed.

When constructing a part, some portions may be created with compositematerial, and some portions may be created with only primary material.The apparatus has the option of creating paths with the compositematerial or with only the primary material. When a composite path iscomplete, it is cut. The next path in the creation of the part may becomposite material, or may be of only extruded primary material.

This embodiment of the method is useful when the secondary material isneeded only in small quantities. This embodiment of the method is alsouseful when the manufacturer requires only the exterior paths of a partto contain composite material, or alternatively, when the exterior pathsare solely primary material intended to finish the surface.

The apparatus may be a hand held device. A simple apparatus with manualmaneuvering and controls may be the optimal embodiment for certainrepairs of existing parts or machinery.

The best mode embodiment is an automated mechanical apparatus. Thisembodiment comprises a means of numerical control for the location ofthe nozzle, and thus the extrusion point. The best mode for numericalcontrol is a robotic arm, but other means of control, including a gantrysystem, are envisioned.

Using a computer independent of the apparatus, a three-dimensionaldigital model of the desired part is created with a computer-aideddesign (CAD) program. The model is stored as a digital file.

The model file is then delivered to a software program designed toconvert the model into paths. This program is called the pathingsoftware and translates the model into G-code. G-code is a numericalcontrol programming language. It organizes a sequence of paths alongwith other coordinated controls in a digital file. A G-code fileextension may be .mpt, .mpf, and .nc, among others. Some of the datastored in G-code for a particular part includes: the starting point,coordinates along a path, and endpoint for each path; the size of thepart; which paths are composite materials; which paths are primarymaterial only; where to cut a path or secondary material; the feed rate;the extrusion rate; and controls for the means for curing.

When the pathing software translates a model into G-code, it takesvarious factors into consideration. Depending on the needs of themanufacturer, certain parameters may influence the pathing sequence.Speed of manufacture, the need for continuous paths of compositematerial, the need for paths of primary material, the differences in theinterior and exterior of a part, the desired interior matrix, and weightof the part are examples.

The G-code stores all of the information listed above, and in acoordinated matter. For example, the extrusion rate is synchronized tothe feed rate, ensuring a uniform ratio of primary to secondary materialthroughout the length of a path. Another example is the coordination ofthe extrusion rate and feed rate with the start and end of a path. Bothare stopped during the time the robotic arm is repositioning the nozzleto the next path starting point.

An external computer is linked to the apparatus through a means of dataconnection. An example may be a universal serial bus. The G-code file istransferred to the apparatus and stored in an electronic storage.

The apparatus is comprised of computer hardware and software necessaryfor the translation of G-code into extruded paths. Hardware andelectronic components include: electronic data storage; microprocessor;random access memory; an external data connection; a digital display onthe apparatus for a message log; motors for pumps, vacuum, compressor,numerical control system, and means for curing; input and output wiringto motors and lights; and connection to a power source.

Software components stored in the electronic storage and run on theprocessor include a primary material processing unit, a secondarymaterial processing unit, a path termination processing unit, an energycuring processing unit, and a numerical control processing unit.

The primary material processing unit controls the functions associatedwith the primary material. This includes the extrusion rate, which ismanaged by a pump connected to a hose between the primary materialreservoir and the extruder. Additionally, the primary materialprocessing unit may control alterations to the nozzle. In alternativeembodiments, the apparatus may possess multiple nozzles or an adjustablenozzle. For these embodiments, the primary material processing unit alsocontrols a means of switching nozzles or adjusting the diameter or shapeof an adjustable nozzle.

The secondary material processing unit controls the functions associatedwith the secondary material. This includes starting and stopping thefeeding of the secondary material, as well as adjusting the feed rateduring the extrusion of a path. In alternative embodiments with multiplespools containing secondary materials, this processing unit controls themeans for switching between secondary materials during the manufacturingof a part.

The path termination processing unit controls the cutting of paths. Thisincludes the cutting of the composite material at the end of a path, thecutting of the secondary material when a path is converting to a primarymaterial only, and the cutting of the secondary material in order toalternate to another secondary material.

The energy curing processing unit controls the means for curing. In thebest mode, the apparatus possesses an ultraviolet light aimed at thepath just after the point of extrusion. During extrusion, the light willturn on and off at the beginning and ending of paths, respectively. Forcertain parts, this processing unit may also administer an intermediatelight intensity.

Alternative embodiments may include the controlling of several means forcuring, possibly several ultraviolet lights around the point ofextrusion, curing the path from multiple angles. Another alternativeembodiment includes a means for curing with an adjustable direction. Theultraviolet light may be mounted on an additional numerical controlsystem affording constantly adjusted angles, which target the path as ittrails away from the nozzle in varying directions.

The energy curing processing unit also controls methods that utilize analternative means of curing. The processing unit will control thedistribution of a chemical catalyst, the activation of a heat source, orthe administration of any of the alternative means for curing listedabove.

The numerical control processing unit controls the means of locating thepoint of extrusion. This processing unit maneuvers the nozzle to thestarting point of the first path, the origin, and extrudes all pathssequentially in relation to that point. The means for numerical controlis adjusted accordingly with the sequence of paths, taking intoconsideration the nozzle's angle of approach in relation to the part.

Prior to manufacturing a part, the manufacturer designates an origin.The origin may be any point on any surface suitable for anchoring thepart during manufacturing. This point of contact is called an anchor.Some parts may require multiple anchor points to support a part duringmanufacturing.

Once the origin is located, the numerical control processing unitpositions the nozzle so that the point of extrusion is at the origin.The primary material processing unit pumps the primary material from itsreservoir through a hose, filling the extruder housing with the primarymaterial. Simultaneously, the secondary material processing unit feedsthe secondary material to the nozzle. The energy curing processing unitactivates the ultraviolet light, and the composite material is extrudedas the numerical control maneuvers along the first path.

When the first path reaches its endpoint, the path terminationprocessing unit cuts the path, and the numerical control positions thenozzle for the start of the next path in the sequence according to theG-code. Paths are continuously extruded and cured until the sequence andthe part is complete.

Alternative embodiments include another software component, a feedbackprocessing unit. This processing unit gathers feedback from multiplesensors concerning the status of the apparatus and the currentlyextruding path. Sensors may include a visual input device, such as avideo camera or infrared scanner, a thermometer, a pressure sensor, andinput from the feeder motor.

During the extrusion of a path, the visual input device monitors thepoint of extrusion and the existing paths, relaying that information tothe feedback processing unit. If the point of extrusion is misalignedrelative to the existing part or the pathing coordinates, thisprocessing unit will realign the extruder or halt the extrusion.

Similarly, information regarding temperature of the composite material,the motors, and the electronics is delivered to this processing unit.Also, information about the rate of extrusion, and pressure in all pumpsand hoses is delivered to processing unit. If any feedback is outsidedesignated parameters, the processing unit adjusts the systemaccordingly to ensure the correct extrusion of the current path. Iffeedback continues to lie outside designated parameters, extrusion ishalted.

An alternative embodiment of the method calls for the curing of certainportions of the composite path at a later time. The energy curingprocessing unit will cure portions of the path upon extrusion, but leavesome portions of the path uncured, or partially cured. The uncuredportions are physically manipulated to interact with a cured portion ofthe part, creating what are called “locking paths”.

The manipulation of the uncured portion of the path may be by ahand-held device. The best mode is an apparatus with a robotic arm onthe extruder housing, which has an appendage suitable for manipulatingthe uncured portion. An alternative embodiment may have an appendage onanother type of numerical control, or simply an appendage connecteddirectly to the extruder housing. Another software component, thespatial manipulation processing unit, controls the movements of theappendage in coordination with the other processes.

The uncured portions of the path are adjusted so they interact with acured portion. For example, the uncured portion may be wrapped around acured portion. When the uncured portions are adjusted to the desiredlocation, they are cured and hardened into their new position. Theability to intertwine the paths increases the strength of the part.

FIG. 6 shows an example part and the steps associated with creatinglocking paths. The drawing shows a continuous composite path extruded ina complex pattern. On this part, there are six u-turns, or loops, whichwere initially left uncured upon extrusion. The first loop 601 isuncured and in its original extruded form. The second loop 602 isuncured and in the process of being manipulated so it bends around acured portion of the part. The third loop 603 is fully bent around acured portion of the part.

The three loops on the anterior side of the part in FIG. 6 all wentthrough the process demonstrated by 601 through 603. When the loops arefully bent around the respective cured portions of the part, they arecured and become locking paths.

FIG. 7 shows a part with several iterations of the same locking paths inFIG. 6 . When manufacturing this part, each loop is bent and curedintermittently as each layer of locking paths are extruded.

The method and apparatus described above affords the opportunity toextrude paths not previously available. The inclusion of a secondarymaterial adds structural stability to the composite path, allowingextrusion into space opposed to gravity, as demonstrated in FIG. 8 andFIG. 9 .

FIG. 8 shows a path extruded in a spiral form. The secondary materialsupports the path while it is being extruded, giving the designer andmanufacturer more freedom in creating the part. Slicing methods ofadditive manufacturing by extrusion require a gravitational base beneatheach layer. To extrude a spiral shaped part by slicing technique,additional material supporting each section of the spiral is required.This constricts the designer, requires more material to print a part,and increases the time of manufacture.

FIG. 9 shows a tension path 901. The composite path is first extrudedonto an anchor 903. Any surface or point may provide an anchor point. InFIG. 9 , the anchor is a vertical plane. The origin of the path adheresto the anchor, allowing the extruder to pull on the secondary materialduring the extrusion.

The addition of a secondary material allows the path to extend intospace opposed to gravity and is useful in the extrusion of pathsrequiring long spans. Additionally, tension forces within a finishedpart provide structural strength.

The initial contact between the proposed part and the anchor mustprovide enough adhesion to support the tension force desired. Paths ofgreater tension may require an additional length of path extruded uponthe anchor, to provide more adhesion. FIG. 9 shows a short length ofpath 902 extruded upon the anchor prior to extending horizontally away.

This initial length, called a foot, may or may not be portion of thefinished part. In situations where the foot is simply functional duringmanufacturing, it is removed after the extrusion process.

FIGS. 10 and 11 show two products, a small electronic device and a boathull, created by the method and apparatus. These two figures demonstratea wide range of applications for the method and apparatus describedabove.

FIG. 10 is a small electronic device with a credit card reader and atouch surface 1001. The main body of the device is comprised ofcomposite paths of carbon fiber encased within polymer resin, asrepresented by the pattern 1002. Cross-sections of the paths comprisingthe body are enlarged to enhance visibility 1003. The use of a carbonfiber and polymer resin composite creates a strong and lightweight body.

The circular surface on top of the device is comprised of compositepaths of metal wire encased within fiber optics encased within polymerresin, as represented by the pattern 1004. Cross-sections of the pathscomprising the touch surface are enlarged to enhance visibility 1005.

Metal wires in the composite paths enable parts to have electroniccapabilities. In FIG. 10 , the metal wires form a touch sensitivesurface. The fiber optics in the composite paths enable the surface toilluminate. For example, when a user interacts with the surface bytouching it, the fiber optics light up providing visual feedbackregarding the interaction.

FIG. 11 is a boat hull 1101, comprised of composite paths of hollowrubber tubing encased within carbon fiber encased within polymer resin,as represented by the pattern 1102. Cross-sections of the pathscomprising the hull are enlarged to enhance visibility 1103. The use ofcarbon fiber and polymer resin in the composite paths provide strengthand lightness. The hollow rubber tubing in the composite paths createair pockets throughout, increasing the lightness and buoyancy of thehull.

What is claimed is:
 1. A continuous-composite printing method formanufacturing an object, the method comprising: providing, with a supplydevice, a supply of polymer to a head; providing, with a providingdevice, a fiber strand pre-pregged with polymer to the head; heating atleast one of the pre-pregged fiber strand and the supply of polymerwithin the head; dispensing a first path of the supply of polymerthrough an outlet end of the head to form a first layer of the object;dispensing a second path of the pre-pregged fiber strand through theoutlet end of the head to form a second layer of the object; using acomputer system, controlling movement of a positioning system toposition an end of the second path onto the first layer; and using thecomputer system, controlling movement of the positioning system to pullthe positioned end of the second path such that the pre-pregged fiberstrand is pulled onto the first layer.
 2. The method of claim 1, furtherincluding, using an energy transfer device to change an energy of atleast one of the dispensed pre-pregged fiber strand and the dispensedsupply of polymer to form the object.
 3. The method of claim 2, whereinthe energy transfer device is mounted to the head.
 4. The method ofclaim 2, wherein using the energy transfer device includes aiming theenergy transfer device toward the outlet end of the head to change anenergy of the pre-pregged fiber strand after dispensing through theoutlet end of the head.
 5. The method of claim 2, wherein using theenergy transfer device includes changing a temperature of at least oneof the dispensed pre-pregged fiber strand and the dispensed supply ofpolymer to harden the at least one of the dispensed pre-pregged fiberstrand and the dispensed supply of polymer after dispensing.
 6. Themethod of claim 1, further including using a desktop printer to performthe method.
 7. The method of claim 1, wherein the positioning systemincludes at least one of a robotic arm and a gantry.
 8. The method ofclaim 1, wherein a combination of (1) controlling the head to press thepre-pregged fiber strand through the outlet end of the head and (2)controlling movement of the positioning system to pull the pre-preggedfiber strand through the outlet end of the head discharges thepre-pregged fiber strand onto the first layer.
 9. The method of claim 1,wherein pulling the pre-pregged fiber strand onto first layer includescreating tension in the pre-pregged fiber strand.
 10. The method ofclaim 1, further including controlling, by the computer system, movementthe positioning system to use the positioned end of the pre-preggedfiber strand as an anchor in pulling the pre-pregged fiber strand ontoat the first layer.
 11. The method of claim 1, further including using afeeder motor of the providing device to feed the pre-pregged fiberstrand to the head.
 12. The method of claim 11, wherein using the feedermotor includes using the feeder motor to press the pre-pregged fiberstrand onto the first layer.
 13. The method of claim 11, wherein usingthe feeder motor includes feeding, by the feeder motor, the pre-preggedfiber strand from a spool storing the pre-pregged fiber strand.
 14. Themethod of claim 11, wherein using the feeder motor includes feeding thepre-pregged fiber strand to the head at a first rate, and the methodfurther includes controlling, by the computer system, movement of thepositioning system to pull the pre-pregged fiber strand at a second ratethat is greater than the first rate.
 15. The method of claim 1, whereinthe pre-pregged fiber strand comprises a plurality of strands.
 16. Themethod of claim 1, wherein heating the at least one of the pre-preggedfiber strand and the polymer includes heating the pre-pregged fiberstrand to a temperature at which the polymer becomes liquid.
 17. Themethod of claim 1, wherein heating the at least one of the pre-preggedfiber strand and the polymer includes heating the supply of polymer to atemperature at which the polymer becomes liquid.
 18. The method of claim1, further including using a cutter connected to the head to cut thepre-pregged fiber strand.
 19. The method of claim 18, wherein the cutteris located upstream of the outlet end of the head with respect to adirection in which the pre-pregged fiber strand is dispensed.
 20. Themethod of claim 19, further including controlling, by the computersystem, the cutter to cut the pre-pregged fiber strand upstream of theoutlet end of the head before dispensing through the outlet end of thehead.
 21. The method of claim 1, wherein the polymer is a plastic. 22.The method of claim 21, wherein the plastic is a thermoplastic.
 23. Themethod of claim 1, further including guiding the pre-pregged fiberstrand from the providing device to the head using a tube connecting theproviding device to the head.
 24. The method of claim 1, furtherincluding controlling a temperature of at least one of the supply ofpolymer and the pre-pregged fiber strand to allow the at least one ofthe supply of polymer and the pre-pregged fiber strand to harden afterdispensing.
 25. The method of claim 1, further including receiving, bythe computer system, a model of the object defining a plurality ofslices of the object, wherein: dispensing the supply of polymer includesdispensing the supply of polymer to form the first layer based on afirst of the plurality of slices; and dispensing the pre-pregged fiberstrand includes dispensing the pre-pregged fiber strand to form thesecond layer based on a second of the plurality of slices.
 26. Themethod of claim 1, wherein: dispensing the first path of the supply ofpolymer through the outlet end of the head includes dispensing the firstpath through a first dispensing port located at the outlet end of thehead; and dispensing the second path of the pre-pregged fiber strandthrough the outlet end of the head includes dispensing the second paththrough a second port located at the outlet end of the head.
 27. Acontinuous-composite printing apparatus for manufacturing an object, thecontinuous-composite printing apparatus comprising: a platform; apositioning system; a supply device that provides a supply of polymer; aproviding device that provides a fiber strand pre-pregged with polymer;a head having an outlet end and configured to receive the supply ofpolymer and the pre-pregged fiber strand and to dispense the supply ofpolymer and the pre-pregged fiber strand through the outlet end; a mountconnecting the head to the positioning system; a heater configured toheat at least one of the polymer or the pre-pregged fiber strand withinthe head; a computer system including a processor operatively coupled tothe platform, the positioning system, the providing device, the supplydevice, and the heater, the computer system configured to: receive amodel of the object defining a plurality of slices of the object;control the supply device to press a first path of the supply of polymerthrough the outlet end of the head to form a first layer of the objectbased on a first of the plurality of slices; control the providingdevice to press a second path of the pre-pregged fiber strand throughthe outlet end of the head to form a second layer of the object based ona second of the plurality of slices; control movement of at least one ofthe positioning system and the platform to position an end of the secondpath onto the first layer; and control movement of at least one of thepositioning system and the platform to pull the positioned end of thepre-pregged fiber strand such that the pre-pregged fiber strand ispulled through the outlet end of the head and onto the first layer.